Method and apparatus for suspendedly supporting a platform

ABSTRACT

A method and apparatus for lifting a platform dependently supported from a member by support arms supportingly connected to the platform and independently reciprocable relative thereto between raised and lowered positions. A force is applied between support arms in engagement with the member and the platform, acting relatively downward on the support arms and upward on the platform. The force is of sufficient magnitude to lift the platform and will move it from a position spaced below the member to a position in contact therewith. The lifting force is preferably provided by a pressurized fluid, such as air. The lifting operation may be utilized to recover vertical slippage between the platform support arms and the member with which they are engaged.

United States Patent Ranger 1 1 June 17, 1975 METHOD AND APPARATUS FORSUSPENDEDLY SUPPORTING A PLATFORM Inventor: Eugene Ranger, East Ridge,Tenn.

Assignee: Combustion Engineering, Inc.,

Windsor, Conn.

Filed: Aug. 1, 1973 Appl. No.: 384,659

U.S. Cl 214/1 BB; 74/22 R; 165/76;

214/1 CM; 214/152; 294/85 Int. Cl. F28g 15/02 Field of Search 214/1 B, 1BB, 1 CM, 152;

{56] References Cited UNITED STATES PATENTS 2,136,255 11/1938 Scanlon294/85 X 3,643,701 2/1972 Wadiak .t 165/76 Primary Examiner-Robert J.Spar Assislanl Examiner-George F. Abraham 5 7 ABSTRACT A method andapparatus for lifting a platform depen dently supported from a member bysupport arms supportingly connected to the platform and independentlyreciprocable relative thereto between raised and lowered positions. Aforce is applied between support arms in engagement with the member andthe platform, acting relatively downward on the support arms and upwardon the platform. The force is of sufficient magnitude to lift theplatform and will move it from a position spaced below the member to aposition in contact therewith. The lifting force is preferably providedby a pressurized fluid, such as air. The lifting operation may beutilized to recover vertical slippage between the platform support armsand the member with which they are engaged,

22 Claims, 10 Drawing Figures SEEEEI PATENTEUJUN 1 7 I975 IIOa IIOb

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FIG. 2

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1 METHOD AND APPARATUS FOR SUSPENDEDLY SUPPORTING A PLATFORM BACKGROUNDOF THE INVENTION The invention relates generally to means for supportinga platform from and beneath a member having holes in the undersurface.More particularly, the invention pertains to a supporting means adaptedto grippingly engage said member while inserted in said holes. Moreparticularly still, the invention pertains to a method and apparatus forrecovering any slippage of the platform and its support means relativeto the member from which it is suspended.

In a variety of environments it may be necessary to provide a platformor carriage from which various types of work can be remotely conducted.Further, it may be necessary to movably suspend the platform fromanother member. It may be further necessary to permit the platform to beremotely moved parallel the member from which it is suspended. Anexample of this situation arises in nuclear steam generators where itmay be necessary to inspect and/or repair some of the tubes containedtherein.

A remotely operated moving platform may allow remote operations to beconducted therefrom without requiring continued or frequent presence ofa human in the steam generator which may be radioactive. Two suchplatforms, capable of remote operation and locomotion are describedrespectively in US. Pat. application Ser. No. 384,658 for REMOTELYMOVABLE PLATFORM by C. T. Ward, D. L. Mathis, F. T. Radcliff and R.Vorwerk filed Aug. 1, I973 and US. Pat. application Ser. No. 384,657 forREMOTELY MOV- ABLE PLATFORM by C. T. Ward, D. L. Mathis, F. T. Radcliffand E. Ranger filed Aug. 1, 1973. Each of these remotely moved platformsmay be suspendedly supported beneath the undersurface of a tube sheet bysupport means extending upwardly therefrom and grippingly engaging thetube sheet or some member affixed thereto. In the preferred embodimentsof the platforms of the above two patent applications, selectivelyexpandable anchors are extensibly connected to the platform. Theseanchors include a finger and a gripper thereabout and moving therewith.The anchors are extended relative to the platform base into the openingsformed by the tubes in the tube sheet. The gripper is then expanded intogripping engagement with the wall of the tube to bear a portion of theweight of the platform base connected thereto. A sufficient number ofanchors are used to always support the platform. Further, the anchorsmay be translated relative to the base in a direction whichsubstantially parallels the plane of the base and the tube sheet inorder to move the platform base substantially parallel the undersurfaceof the tube sheet. By selective extension, expansion, retraction andtranslation of various of the anchors, it is possible to walk theplatform across the undersurface of the tube sheet to align it, or awork station portion, with a tube or tubes to be inspected and/orrepaired.

The supported positioning of platform base relative to the tube sheetshould be such as to maintain a constant spacing between the base andthe tube sheet, and this would be possible if gravity forced theplatform toward the tube sheet, or if the grippers of the anchors werealways uniformly inserted in the tubes and gripped sufficiently toprevent any slippage, regardless of weight or work loading. However, inpractice, the

platform will generally be used where it depends below the tube sheet,such that gravity acts against the anchor grippers. Further, the workoperations may include forcing a plug into the tube end which wouldfurther downwardly load the platform. Further still, it may be necessaryfor the platform to be "stepped" hundreds or even thousands of times andsmall slippage with each step could accumulate to a significant extent.If, in any of these instances, the extent of slippage accumulatedsufficiently to remove the grippers from gripping engagement with thetube walls, the platform would fall face free of the tubes and tubesheet, possibly damaging it and requiring human presence forreinstallation.

SUMMARY OF THE INVENTION According to the invention there is provided amethod and apparatus for remotely lifting a platform, or at least thebase portion thereof, when it is supported beneath a tube sheet byanchor means extensibly connected thereto for insertion into grippingengagement with walls of openings in the undersurface of the tube sheet.

Broadly, the invention includes means and a method of operating themeans which prevent a dependently suspended platform from falling out ofsuspended engagement with the member from which it is suspended.Further, the invention provides a method and apparatus for lifting aplatform base relative to a member from which it is suspended tomaintain it in close proximity therewith therebelow. More specifically,the invention provides means and a method of operation thereof whichrecovers relative slippage between the platform support and the memberwith which it is grippingly engaged, this function being accomplishedeither when the platform remains fixedly positioned laterally of thetube sheet or when it walks" or steps" laterally thereof. Further, theinvention may be utilized to maintain the base portion of the platformproximate or in contact with the tube sheet undersurface, particularlywhen all of the support means grippingly engage the tube sheet.

The platform includes a base portion and at least two, and preferablyfour or more, anchor or support means of the finger and gripper type forselective insertion into gripping engagement with the walls of holes inthe tube sheet undersurface, A support means typically comprises anupwardly extending finger mounted on a finger piston reciprocable in anupwardly extending cylinder carried by the platform base, a resilientsleeve about the finger, and sleeve expanding means including acompression jaw surface and second piston about the finger below thesleeve and above the finger piston and vertically movable relative tothe finger and sleeve to longitudinally compress and radially expand thesleeve. The sleeve, when inserted in a hole in the tube sheet andexpanded, will grippingly engage a wall of the hole.

The finger and its piston may be moved upward relative to the cylinderand base carrying the resilient sleeve for insertion in a hole by afirst force applied between the piston and cylinder. The sleeve may beexpanded by a second, repulsive force applied between the finger pistonand the second piston. The second piston, and accordingly the fingerpiston, may be moved downwardly relative to the cylinder and base, evenwhen said second force exists between the pistons and the sleeve isengaging a hole wall, when a third force of greater magnitude andopposite direction to the first force is applied between the secondpiston and the cylinder. This effects a lifting or cinching of the baserelative to the tube sheet if the third force is of suffcient magnitude.In each instance, the force may be provided by a pressurized fluid, suchas air.

The third force may be continuously applied during the time that allsupport means are in gripping engagement with the tube sheet to maintainthe platform base in close proximity or in contact with the tube sheetundersurface. Further, the third force may be applied to one or moresupport means in gripping engagement with the tube sheet during suchtime as other support means are being extended and inserted into holesand expanded into gripping engagement. This operation insures maximuminsertion of the newly implanted support means and provides means forrecovering slippage of the support means. This latter function may beaccomplished while the platform remains laterally stationary relative tothe tube sheet or it may be accomplished as part of a stepping operationif the support means have a stepping capability. If attendant to a stepping operation, it may be desirable for certain platform constructionsto avoid or remove application of said third force during the lateralmovement of the platform to prevent sliding contact between therelatively mov ing platform and tube sheet.

In one embodiment, a spacer between the finger piston and second pistonof each support means defines a minimum chamber length therebetweenwhich approximates the distance between the platform base and the uppergripping surface of the resilient sleeve when it is at its upwardlyextended limit. A fluid admitting port for applying the sleeve expandingforce between the finger piston and second piston is located in thecylinder wall closely above the finger piston when it is fully extendedsuch that it will remain in registry with the chamber between thepistons even when they are partially withdrawn by the cinchingoperation.

In another embodiment, the spacer between the pistons may be greatlyreduced in length, or eliminated, by introducing the sleeve expandingfluid to the region between the pistons from a port and conduit whichmove with one of the pistons.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cutaway perspective viewof a steam generator showing the platform incorporating the novelsupport system operatively positioned therein.

FIG. 2 is a transverse section of the steam generator taken along line2-2 of FIG. 1 to show the pattern of tube ends.

FIG. 3 is a plan view of the mobile platform incorporating the novelsupport system.

FIG. 4 is an elevationai view of the mobile platform depicted in FIG. 3.

FIG. 5 is a sectional view ofa typical support member of FIG. 3 takenalong line 55 therein.

FIG. 6a is a view of a support member, showing it inserted in a tubeprior to expansion.

FIG. 6b is a view, similar to 60, however showing the support memberfollowing expansion into gripping engagement with the tube wall.

FIG. 7a is a view similar to FIG. 6b, however showing an increasedvertical spacing between the tube sheet and the base portion of theplatform.

FIG. 7b is a view similar to FIG. 7a, however showing reduction of thevertical spacing through operation of the invention.

FIG. 8 is a view similar to FIG. 7b, however showing an alternate meansfor delivering air to the region between the two pistons of the supportsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I, thereis depicted a typical nuclear steam generator 10 including a vessel 12having a large number of tubes 14 supported therein and terminating atone or both ends in a tube sheet l6. In the steam generator 10 depicted,the vessel 12 and tubes 14 are generally vertically oriented with thetubes being of an inverted U shape with both ends of the tubesterminating in or slightly below the generally horizontally extendingtube sheet 16. The tubes 14 are hollow and circular in cross section andextend through generally cylindrical passages extending verticallythrough the tube sheet 16 and are snugly and securely affixedtherewithin. Tubes 14 have an inside diameter of 0.75 inch. The tubes 14terminate at or slightly below the lower surface of tube sheet 16creating circular, vertically extending openings extending upwardly inthe tube sheet.

Tube sheet 16 is supported within vessel 12 in spaced relationship withthe bottom of the vessel. The tube sheet may be 10 to 15 feet indiameter and receives both the hot and cold ends of as many as 9,000primary coolant U tubes 14. The region below tube sheet 16 may bedivided into halves by a vertical divider 20 and a manway 24 in vessel12 on each side of divider 20 permits human access to the steamgenerator below tube sheet 16. A manway 24 may have a diameter of about16 inches.

The tubes 14, and accordingly the ends thereof, are positioned such thatopenings 18 are in a particular pattern which is fairly uniform andrepetitive. A carriage, or platform 32 has been developed which issuspended from and thus supported by, the tube sheet 16 or tubes 14 andis remotely actuable for movement parallel the tube sheet. This movementis utilized to move a work station contained with the platform intoalignment with various, and preferably all, of the openings 18.

Remotely movable carriages or platforms of the type generally describedabove are described in greater detail in U.S. Pat. application Ser. No.384,658 for RE- MOTELY MOVABLE PLATFORM to C. T. Ward, D. L. Mathis, F.T. Radcliff and R. Vorwerk filed Aug. 1, 1973 and Ser. No. 384,657 forREMOTELY MOV- ABLE PLATFORM to C. T. Ward, D. L. Mathis, F. T. Radcliffand E. Ranger filed Aug. 1, 1973 mentioned earlier herein. The platformsdescribed in the abovementioned applications generally utilized two ormore anchor or support means which could be remotely engaged anddisengaged from the tube sheet to support the platform. Further, one ormore of the anchors or support means is translatable relative to theplatform base in a direction parallel said base to effect locomotion ofthe platform. The invention will be described as embodied in one of theplatforms described in the aforementioned applications, however, it willbe appreciated that it will also be similarly applicable to the otherplatform described therein.

One typical pattern in which the ends of the tubes 14 are arranged intube sheet 16 is seen in FIG. 2. This pattern of tube 14 ends, orsimilarly, of openings I8, has a triangular pitch. By triangular pitchit is meant that the straight rows of openings 18 which intersect oneanother and share a common hole do so at an angle other than 90. In thesteam generator here described, this angle of intersection is l20 (orits supplement 60). as defined by directional arrows 28 and 30 in FIG.2. This arrangement comprises a continuous series of equilateraltriangles adjacent rows or offset from one another to create thispattern. In another pattern, not shown here, the openings 18 may have asquare or rectangular pitch in which rows of holes which intersect oneanother and share a common hole do so at an angle of 90.

Typically, the internal diameter of the tube 14 which generally definesopening 18 is about three quarters of an inch. The distance betweencenters of adjacent tubes 14 having the above-mentioned uniform spacingis one inch. This distance may be referred to later herein as the unitdistance,

The invention is associated with a platform or carriage 32 capable ofbeing remotely moved laterally sub stantially parallel to the lowersurface of tube sheet 16 and which is dependently supported from and bythe tube sheet. Carriage 32 in this embodiment is intended for use as awork platform from which various remotely controlled operations may beperformed. As an example, carriage 32 may serve as a platform or supportfor nondestructive testing equipment such as an eddy current probe.Alternatively or additionally it may be used as a platform from whichrepair procedures on a partic ular tube 14 may be remotely performed.Additional explanation of such capabilities will follow a description ofthe carriage 32.

A preferred embodiment of carriage 32 is depicted in FIGS. 3 and 4 andcomprises essentially a base portion 34 and a supporting mechanism 36according to the invention, connected to said base 34. Mechanism 36includes means for supporting the carriage below the undersurface oftube sheet 16. A stepping mechanism forming part of base portion 34 andto which support mechanism 36 is connected may provide means forpropelling base 34 and accordingly carriage 32 parallel the undersurfaceof tube sheet 16.

The base 34 of carriage 32 includes a member 38 which is preferably of astrong light material such as aluminum or magnesium and is in plan viewin the form of a pair of E's back-to-back and having a short crossarm atthe outer end of the middle arm of each E. The lateral extent of basemember 38 may be some eight to ten inches in each direction and it maybe an inch or more in thickness. A pair of rollers 40 are mounted ineach diagonally opposite laterally outer corner of base member 38 forrotation about a vertical axis. The rollers 40 are horizontally disposedfor rotation about a vertical axis provided by mounting bolts or pins42. Each pin 42 is captively retained on or in base member 38 againstsubstantial vertical or lateral motion relative thereto and a roller 40is retained on each pin against substantial vertical or lateral motionrelative thereto. A limited amount of vertical freedom of roller 40relative to base member 38 may be desirable to permit limited verticalmovement between base member 38 and sliders 46a and 46b. Each roller 40is free to rotate relative to base member 38, as mounting pins 42 mayalso. Rollers 40 are generally above base member 38. A pin 42 andassociated roller 40 is positioned near the extremity of each arm of theback-to-back E5 of base 34 and at the extremities of the crossarms onthe middle arms of the ES. These portions of the base 34 and accordinglythe rollers 40 are positioned and spaced such that a pair of rollers arein laterally spaced opposition at each corner of the base.

The stepping mechanism on base 34, and accordingly carriage 32, includesa pair of sliders 46a and 46b, which house supporting mechanisms 36which include fingers 48a and 48b respectively and gripping sleeves 50aand 50b respectively. The sliders 46a and 46b each comprise a pair oflaterally spaced parallel vertically extending housing members 52connected at or near their upper ends by a transversely extending rigidconnecting arm 54. Arm 54 and housing members 52 may be integrallyformed of aluminum or magnesium or the like. Each housing member 52includes an upwardly or vertically extending cylinder therein which isclosed at its bottom and opens upwardly to be used in a manner describedhereinafter. The cylinders 56 in slider 460 will be designated cylinders56a and correspondingly those in slider 46b will be designated cylinders56b. Work stations or locations such as cylindrical bores or tubes 58may extend through or be affixed to each slider 46a and 46b at or nearlaterally opposite ends thereof preferably outward of cylinders 56.Tubes 58 might additionally or alternately be positioned on or withinbase member 38 along its outer perimeter. However certain advantagesobtain if tubes 58 may be variably positioned relative to the base, asby movement of the sliders 46.

Sliders 46a and 46b are movably connected with base member 38, or moreaccurately, are connected in a manner to movably support the base bymeans of rolling contact with the rollers 40. Each slider 46 is of suchlength laterally that it concurrently extends between a pair of rollers40 at diagonally opposite ends of base member 38 and is of such lateralwidth that it is in supported or supporting contact with the pair ofrollers. Preferably each slider 46 is wider than the space between apair of rollers 40 and includes a pair of horizontally extending groovesor guides 60 along opposite sides thereof parallel the longitudinalextent of the slider at or near each end thereof. Guide grooves 60 eachreceive a portion of the outer periphery ofa roller 40 therewithin andare in rolling and supported contact therewith. In this manner sliders46a and 46b may be translated or reciprocated in a direction whichsubstantially parallels the plane of base member 38 and base 34.

The connecting arm 54 of one slider 46 extends or crosses over the armof the other slider in noninterfering relationship, both above basemember 38. The sliders 46a and 46b cross one another at an angle whichcorresponds to the angle made between intersecting rows of holes 18 inthe tube sheet 16. For the tube sheet shown this angle is conveniently120 (with a supplementary angle of 60) in accordance with the anglerevealed by the intersectional arrows 28 and 30 in FIG. 2. It might befor tubes having a square or rectangular pitch. In the rows of holes 18paralleling the directional arrows 28 and 30 each hole in the rows inboth directions is uniformly spaced from the immediately adjacent holein that row in the spacing is the same in both intersecting directionsand corresponds to the unit distance earlier mentioned. This uniformityof spacing of holes 18 pennits a uniformity of spacing of the supportmeans which include fingers 48 and gripping sleeves 50 to be describedlater. Further, this uniformity of spacing of holes l8 permitsuniformity in the length of lateral thrust of each slider relative tobase 34. The fingers 48 and gripping sleeves 50 at opposite ends of eachslider 46 are spaced from one another by some integer number times theunit distance between centers of adjacent pairs of holes 18. Typicallythis spacing might be five to ten times the unit distance. Further, theprobe tubes 58 are also spaced from fingers 48 and gripping sleeves 50by an integer multiple of the unit distance, usually one. Tubes 58in thedepicted embodiment are centered in the same plane that extendsvertically through the centerline of the fingers 48 in cylinders 56 of aslider. Each slider 46 is of sufficient length that it may bereciprocated longitudinally an extent corresponding to one, or possiblytwo, times the unit distance between an adjacent pair of holes 18 whilein supported or supporting engagement with rollers 40. Thisreciprocation or translation of each slider 46a and 46b is effected bymeans of respective motors, preferably linear motors, such as fluidactuated piston and cylinder combinations 62a and 62b respectively. Itwill be appreciated that such linear motion might also be obtained byconverting the rotary motion of a motor to linear motion, as with a rackand pinion. Each piston and cylinder combination 62a and 62b ishorizontally disposed and the cylinder portion thereof is affixed to thebase 34 as by being rigidly joined to base member 38.

Cylinders 62a and 62b are oriented to parallel the respective sliders 46with which they are associated. A piston rod 64 extends from each of thepistons associated with the combination 62a and 62b and is nonyieldinglysecured at its outer end to a flange 66a or 66b respectively associatedwith slider 460 or 46b. Flange 66a is fixedly secured to slider 460 nearone end thereof and flange 66b is fixedly secured to slider 46b near oneend thereof. Actuation of the piston and cylinder combination 620 and/or62b thus serve to reciprocate or translate the respective sliders in anobvious and well known manner. Each slider 46 may have two discretelateral positions relative to base 34, or possibly three such positions,as disclosed in either of the aforementioned patent applications. ifonly two positions are to be used piston and cylinders 62 will beconventional double acting pistons requiring two air conduits 68a or 68band 700 or 70b shown in FIG. 4 connected respectively through controlvalves 69a or 69b and control valves 71a or 7117 to air supply 73. Ifthe piston and cylinder combination is to have a two stroke capability(three positions), then a third conduit to each combination will berequired. A two stroke, three position piston and cylinder combinationis described in the aforementioned patent applications to whichreference may be made for any further details. Each stroke length of thepiston and cylinder combination 62 is made equal to the unit distance"between centers of an adjacent pair of holes 18.

A description of the novel supporting mechanism 36 for the carriage 32and the operation thereof will now be undertaken. Referring to FIG. thehousing member portion 52 of a slider 460 or 46b is shown with avertical section taken through the center of cylinder 56 therein. Eachcylinder 56 may be formed by a cylindrical vertical bore in a housingmember 52. This bore may be made from the underside of the housingmember and extend upwardly part way therethrough. A smaller boreconcentric with cylinder 56 may extend the remainder of the way upwardfrom the cylinder through housing member 52. The bottom end of the boreforming cylinder 56 will be sealingly closed, as by a cover plate 74. Acylinder 56 might typically be three or more inches in length with thesmaller diameter concentric bore extending upwardly therefrom beingnearly the same length, or somewhat less.

Typically a cylinder 56 might be about one inch in diameter with thesmaller bore thereabove being about one-half an inch in diameter.

A finger piston 76 is radially sized for sliding relationship withincylinder 56 axially thereof. A rigid rod or finger 48 is affixed to andextends upwardly from finger piston 76. Each piston 76 includes anO-ring there about for sliding sealing contact between the piston andthe wall of cylinder 56. Piston 76 is movable within cylinder 56 betweena lowered position in which it contacts the bottom end of the cylinderand a raised position thereabove but below the upper end of thecylinder. The length of finger 48 is such that it extends more than aninch, and preferably two inches or more, above the upper surface ofhousing member 52 of a slider 46 when the piston 76 is in its raisedposition. Further, this length is such that the upper end of finger 48is flush with or below the upper surface of the housing member when thepiston 76 is in its lowered position. Finger 48 includes a downwardlyfacing jaw 80 at or near its upper end. Jaw 80 may be formed as anintegral part of finger 48 or by means of an enlarged nut threadedlysecured thereto.

Means for grippingly engaging the inner wall or walls of openings 18defined by tubes 14 are associated with and carried by the finger 48. Inthis embodiment these engaging means comprise a deformable grippingsleeve 50 disposed about an axially extending portion of finger 48 andof somewhat smaller outer diameter than the diameter of the small boreabove cylinder 56. A gripping sleeve 50 may be tubular and comprised ofa flexi ble or deformable material or elastomer, such as gum rubber, apolyurethane or the like. The material of sleeve 50 is preferably onehaving a relatively high coefficient of friction.

A rigid tubular sleeve 82 slidably encircles each finger 48 along itslower extent below the deformable gripping sleeve 50 and also extendsradially outward beyond the inner diameter of the gripping sleeve, thusforming an upwardly facing lip or jaw against the undersurface of thegripping sleeve 50. A piston 84 is affixed to rigid sleeve 82 near itslower end and slidably encircles finger 48. Each piston 84 is ofessentially the same diameter as the piston 76 associated with thefinger 48 and includes an O-ring thereabout for sliding fluid sealingcontact between the piston and the wall of cylinder 56. In thisarrangement piston 84 is positioned intermediate piston 76 and the upperend of cylinder 56 and, accordingly, will contact the upper end of thecylinder when the finger piston 76 is driven upwardly to its raisedposition. The underside of piston 84 may serve as a stop limit forfinger piston 76 to define the raised limit position of the latterpiston. it may be desirable for reasons to be described hereinafter toprevent the entire upper surface of piston 76 from contacting the lowersurface of piston 84 in order to maintain a fluid receiving chambertherebetween, therefore spacer means such as the raised land 86 on theupper side of piston 76 is provided. The spacer, in this instance land86, is significantly smaller in diameter than the diameter of either ofpistons 76 or 84. The spacer might also have been a free standing shimor washer encircling finger 48 below piston 84 or it might have been adownwardly extending land affixed to the bottom side of piston 84. Land86, in one embodiment, is of an axial length equal to or somewhat lessthan the distance from the upper surface of housing member 52 to theupper extent of the active gripping portion of sleeve 50 when pistons 76and 84 are in their raised limit positions.

A small land might also be provided on the upper surface of piston 84 tomaintain it slightly spaced below the upper end of cylinder 56 when itand piston 76 are in their raised limit positions to facilitateintroduction of driving fluid thereabove.

Finger 48 and gripping sleeve 50 are shown in the lowered position inFIG. 5. In order for sleeve 50 to grippingly engage the wall of anopening 18 it is necessary that the finger 48 and sleeve 50 be upwardlyextended to the raised limit position determined by piston 76 and thatthe sleeve 50 then be radially expanded by axially separating pistons 76and 84 relative to one another. By axially moving pistons 76 and 84 awayfrom one another the upper surface of rigid sleeve 82 and the downwardfacing surface of jaw 80 are moved relatively toward one another axiallycompressing sleeve 50 therebetween. Sleeve 50 may not move radiallyinward because of the presence of finger 48 thereat and accordinglyexpands radially outward. lf carriage 32 has been previously placed,possibly manually, closely below the undersurface of tube sheet 16, withfingers 48 aligned with openings 18, the upward extension of finger 48and sleeve 50 and the subsequent expansion of the latter member willresult in the sleeve grippingly engaging the wall of a tube 14 intowhich it was inserted.

FlG. 6a depicts carriage 32 closely below and preferably with baseportion 34 in contact with the undersurface of tube sheet 16 and showsthe finger 48 and its gripping sleeve 50 in its raised limit positionand fully inserted within an opening 18 defined by tube 14. FIG. 6bdepicts the gripping sleeve 50 in its radially expanded configurationand shows it in gripping engagement with the interior wall ofa tube 14.The outside diameter of sleeve 50 in its relaxed state is enough smallerthan the inside diameter of tube 14 to permit its easy insertiontherewithin but is sufficiently large to provide good radial expansioninto gripping contact with the tube when axially compressed andshortened by [-20 percent ofits length. Typically the outside diameterof gripping sleeve 50, when relaxed, is 0.56 inch.

The means for actuating pistons 76 and 84 preferably include pressurizeddriving fluid, and more particularly, a pressurized gas such as air. Itwill be appreciated however that other means such as springs might beused in combination with pressurized air. Raising of the pistons 76 and84 to the raised limit positions is effected by admitting air tocylinder 56 below piston 76 when it is in its lowered limit position.This is accomplished by connecting one end of a conduit 88 to port 90 inthe lower end of cylinder 56 and connecting the other end to arelatively low pressure source of air 92 through a control valve 94.

In order to effect axial compression of sleeve 50 and to obtain thenecessary radial expansion, pressurized air is admitted to the region orchamber between pistons 76 and 84 when they are in their raised limitpositions. This is accomplished in one embodiment by connecting arelatively high pressure source of air through control valve 102 inconduit 96 to port 98 in cylinder 56. Port 98 is located just above theupper surface of piston 76 when it is in its raised limit position.

The pressures involved will of course depend on the quality and geometryof sleeve 50, the active surface areas of the piston, and the weight andfriction of the elements to be moved, however in the embodimentdescribed a pressure of about 25 pounds per square inch at source 92 hasbeen found adequate to extend finger 48 and insert it within a tube 14and a pressure of some 100-150 pounds per square inch has been requiredof source 100 to effect the necessary separating force between the twopistons to expand the sleeve 50 into snug gripping engagement with thetube.

The several control valves discussed and to be discussed herein areconventional three-way valves which utilize only two operativepositions, one being that which admits air from the source to thecylinder and the other being that which vents air from the cylinder tothe atmosphere. These valves may be manually or automatically operated,as is well known. To release sleeve 50 from gripping engagement withtube 14 it is only necessary that valve 102 be vented to the atmosphereremoving the separating force between piston 76 and 84. Finger 48 mightdescend to its lower limit position when control valve 94 is vented tothe atmosphere following venting of control valve 102, however, frictionbetween the pistons and cylinder may require that an additionaldownwardly applied force be applied. This additional downward forcewould normally be applied to piston 84 and would not normally be ofgreat magnitude. This may be accomplished by admitting air to cylinder56 above piston 84 through a conduit 104 connected at one end to a port106 in cylinder 56 above sleeve 84 in its raised limit position andconnected at its other end to a source of air 108 through valve 110. Airsource 108 would normally have to be at a pressure no greater than l0-25pounds, however, according to the invention, a greater pressure may bedesirable to accomplish the lifting of carriage 32 in the manner to behereinafter described.

Referring to FIG. 7a, finger 48 and gripping sleeve 50 are shownrespectively in their fully extended and fully expanded configurations,however, it will be noted that they are not fully inserted within tube14 to an extent which brings the upper surface of housings 52 of asliders 46 into contact with the undersurface of tube sheet 16. Thiscondition may result either because carriage 32 was spaced somewhatbelow tube sheet 16 when finger 48 was initially extended and inserted,or because it has slipped downward relative to tube sheet 16 and tube14. The latter-mentioned slippage may arise from excessive loading ofcarriage 32 as during a work operation in which an instrument or plug isinserted into a tube 14 and the carriage is used as the support platformfrom which this work operation is launched or a slight amount ofslippage may occur during the stepping operation in walking the carriageacross the undersurface of the tube sheet.

it is preferable that carriage 32, and specifically base portion 34thereof, remain as closely adjacent the undersurface of tube sheet aspossible, both to serve as a relatively constant reference point fromwhich work operations may be conducted and additionally to avoid theproblem of lateral misalignment of a test probe or the like which may belaunched from base 34 into a tube 14. Further, if the spacing resultsfrom slippage of the gripping sleeve 50 and is repetitive with time thenit will be necessary to recover some or all of this slippage to preventthe carriage 32 from ultimately falling free of tube sheet 16.

To eliminate this greater than minimum spacing between the tube sheet 16and the base portion 34 of carriage 32 and/or to insure maximuminsertion of finger 48 and sleeve 50 into tube 14, the inventionprovides means and a method for lifting base 34 relative to tube sheet16 and/or fully inserting finger 48. Firstly, the pressure of air fromsource 108 admitted to cylinder 56 through port 106 is sufficientlygreat to force piston 84 and accordingly piston 76 downwardly relativeto the cylinder 56 and base 34, or stated another way, to force the base34 upwardly relative to piston 84. This pressure will depend principallyupon the weight being supported by finger 48 and gripping sleeve 50 andthe frictional forces between the pistons and the wall of cylinder 56.The greater the number of supporting means in gripping engagement withtubes 14 and tube sheet 16, the less the amount of weight supported byeach individual support means. in the embodiment being described inwhich normally at least two supporting means are always in engagementwith the tube sheet 16 a lifting force of some 20-50 pounds at eachfinger 48 is quite sufficient. As the effective work area of the uppersurface of piston 84 is about three quarters of an inch, an air pressuregreater than 30 psi, typically about 70 psi, has been found to beadequate. Such pressures may of course be adjusted to suit theparticular design and weight. The pressure of air required to separatepistons 76 and 84 might have to be increased somewhat to accommodate theincreased downward force on finger 48 and sleeve 50 needed to raise andhold base portion 34. FIG. 7b shows carriage 32, or more specificallyhousing member 52 of slider 46 thereof, in contact or nearly in contactwith the undersurface of tube sheet 16 following the above-mentionedintroduction of air to cylinder 56 through conduit 104. This operationmay be termed a "lifting" or cinching" operation.

By considering the extent to which the gripping sleeve 50 might extendabove the uppermost surface of base 34 or housing 52 when fully raised,it will be seen as depicted in FIG. 7a, that the base 34 and housing 52might descend to a spacing of an inch or more below the undersurface oftube sheet 16 if the gripping sleeve 50 slips somewhat. in such instancethe pistons 76 and 84 will move downward relative to cylinder 56 by anequivalent amount during a cinching operation. It is for this reasonthat, in one embodiment, the spacer land 86 on piston 76 is placedbetween the two pistons and the port 90 is positioned near the uppersurface of finger piston 76 in the latters raised limit position. Bymaking the land 86 of an axial length which approximates the distance orspacing between the upper surface of housing member 52 and the upperextent of the active gripping portion of sleeve 50 when pistons 76 and84 are in their raised limit positions, port 98 may move upward relativeto piston 76 and 84 by that distance during a cinching operation andstill remain in fluid com munication with the chamber between spacedpistons. This is true even for the maximum amount of cinching movement.so long as the sleeve 50 was initially in gripping engagement with atube 14. While the length of the spacer land 86 does not effect thelength of the stroke of finger 78 it does require that cylinder 56 bemade axially longer than would otherwise be the case for a particularstroke length without the spacer.

As an alternative to the spacer land 86, the increased length and weightof cylinder 56 and the precise positioning of port 98, there is depictedin FIG. 8 an embodiment of the carriage supporting means in which theair conduit 96 is connected to a hollow rigid tubular conduit 97 whichin turn is carried by and moves with piston 76. Conduit 97 is connectedat one end to conduit 96 remote from air source 100 and is securelyconnected at its other end to finger piston 76 at the underside thereofand is preferably concentric therewith. A passage or port 98' extendsfrom the end of conduit 97 through piston 76 and possibly into finger 78and opens or exits into the region or space between pistons 76 and 84.Rigid conduit 97 slidably passes through a central opening in coverplate 74 across the lower end of cylinder 56. An O-ring seated inhousing member 52 or plate 74 at the lower end of cylinder 56 fluidlyisolates the cylinder 56 from the atmosphere while allowing reciprocablemotion of the conduit 97 relative thereto. Conduit 97 may be of amaterial such as stainless steel. A downwardly extending sleeve 101 isaffixed at its upper end to the undersurface of cover plate 74 andextends downwardly about conduit 97 to protect it. By delivering thedriving fluid to the region between pistons 76 and 84 in this latterdescribed manner, port 98 will always remain in registry with the regionbetween the pistons regardless of their positionings relative tocylinder 56. It may be desirable to retain a short axially extendingspacer between the pistons to insure at least a minimum spacetherebetween.

The operation of carriage 32 and more specifically, of the support meansincluding fingers 48 and gripping sleeves 50 will now be described. Thedescription is equally applicable to the different embodiments forintroducing air through port 98 or 98'. As described more thoroughly inthe earlier mentioned patent applications, fingers 48 and grippingsleeves 50 are divided functionally into two independent groups with theelements of a group being controlled preferably in unison. The supportmeans associated with one such group have been given the subscript a andthose associated with the other group have been given the subscript b.Structurally the supporting means of one group are identical to those ofthe other group, however their sequence of operation may be varied asdescribed below.

In the description above relative to FIGS. 68, no subscripts wereassigned to the several air conduits, control valves and portsassociated with the cylinder and pistons under discussion. It will beappreciated that if these elements are associated with a cylinder 56a ofone functional group, they would bear the a subscript and thoseassociated with a cylinder 56b of the other functional group would hearthe b subscript. For purposes of discussing the operation of the supportmeans in the two different functional groups, the a and b subscriptswill be used. It will be appreciated that the air supplies 92, 100 and108 may be common to both groups. Further there might only be a singleone of each control valve 94, 102, and 110 associated with the severalcylinders 56 of a functional group, with distribution of the airoccurring between a valve and the several cylinders for unity ofcontrol.

First, platform 32 will be considered as remaining laterally stationaryat a particular location below tube sheet 16. As mentioned earlier, itis preferable that the carriage 32 and particularly the base portion 34thereof be positioned vertically closely below or in contact with theundersurface of tube sheet 16 to provide a constant and reliablereference from which to launch or conduct work operations. In thisconfiguration some, and probably all, of the support means which includefingers 48a and 48b in gripping sleeves 50a and 50b, will be in grippingengagement with tubes 14. This will mean that air is being provided tothe region between pistons 76 and 84 from source 100. Concurrentlytherewith, air will be admitted to cylinder 56 from source 108 throughconduit 104 and ultimately port 106. This air is of sufficient pressureas mentioned earlier to effect relative longitudinal motion between thepistons and cylinders housed in member 52, with members 52a and/or 52brising until they contact the undersurface of tube sheet 16. At thispoint control valves 110a and 11011 and 102 a and remain open to retainthe supporting means in gripping engagement within the tubes 14 and tocinch the carriage up closely against the undersurface of the tube sheetwhile any work functions are performed.

As a modification of the above-described procedure some, but not all, ofthe gripping sleeves 50 may be released from gripping engagement withtheir associated tubes 14. For instance, it will be assumed that thegripping sleeves 50 of the b subscripted functional group are released.This is effected by operation of valves 10211 to disconnect source 100from cylinders 56b and vent that region of the cylinder to theatmosphere. This is accomplished prior to the introduction of airthrough port 106b. Source 108 is subsequently connected with cylinders560 through conduits 104a and ports 106a to lift the base 34 relative tothose fingers 48a in gripping sleeves 50a which remained in grippingengagement with tubes 14. The support means bearing the disengagedgripping sleeves 50b will be raised to their upper limit throughadmission of air to cylinders 56!; via ports 90b and are subsequentlyreexpanded into gripping engagement with the tubes 14 by application ofair from source 100 through ports 9812. In this manner those supportmeans which were released from gripping engagement will have beenreinserted to the maximum depth within their particular tubes 14. Thosesupport means which originally remained in supporting engagement withtubes 14 may now be released from gripping engagement with the tubes byventing through ports 98a and valve 1020. These support means may nowalso be extended to their raised limit position and reexpanded such thatall support means will now be fully extended and fully inserted withinthe various tubes 14 and gripping engagement therewithin.

A somewhat similar procedure is followed in stepping the platform 32laterally of the tube sheet 16 and is described hereinafter. Theoperation will be assumed to begin from a condition in which all sleeves50 are expanded and the carriage base 34 is cinched up against the tubesheet undersurface by means of air pressure from source 108 admitted tothe cylinders 56 through ports 106.

While maintaining expansion pressure on the pistons of cylinders 56athrough ports 98a, the expansion pres sure is released from the pistonsof cylinders 56b by venting through ports 98b and control valves l02b.If

the cinching pressure has been maintained in all cylinders 56 throughports 106 during this operation, both pistons 76b and 84b in cylinders56b will be moved to their lower limit positions. Then the cinchingpressure may be removed from some or all cylinders 56 by venting throughports 106 and control valves 110. This release of cinching pressuremight have been occurred prior to or concurrent with the above-mentionedrelease of the expansion pressure. In either event, the gripping sleeves500 will now remain in gripping en gagement, fingers 48b are in theirlowered positions, and the platform 32 will be released from its cinchedposition, for easy lateral movement relative to tube sheet 19. At thispoint, the platform is ready to be stepped laterally of tube sheet 19.It should be noted that the aforementioned release of the cinchingpressure from cylinders 56 a will be necessary only if there will besome sliding contact or interference between the sliders 460 or 46b andthe underside of tube sheet 16 during the stepping operation. If, asnoted earlier, some degree of vertical freedom exists between basemember 38 and sliders 46a and 46b, it will not generally be necessary torelease the cinching pressure or force from that group of cylinders (560above) which are to remain in gripping engagement with the tube sheet 16during the stepping operation. Rather. the slider (46b above) which willmove laterally relative to tube sheet 16 drops away from the tube sheetby the amount of limited vertical freedom provided between it and basemember 38. This allows a clearance between the slider which movesrelative to the tube sheet during the stepping operation.

Because sleeves 50a remain inserted and expanded in tube sheet 16, theirslider 460 must remain fixed relative to the tube sheet. However, slider46b may be moved relative to slider 46a and tube sheet 16 by actuatingpiston and cylinder 62a to move the base 34 and slider 46b in adirection parallel the extent of slider 46a. Alternatively, if the stepis to be parallel the extent of slider 46!), piston and cylinder 62bwill be actuated moving slider 46b relative to base 34 and tube sheet16. This latter mentioned operation might be considered a half-step asit moves only the slider and not the base and carriage. ln either event,the fingers 48b of slider 46b will now be aligned with a new" pair oftube openings 18. Air will be reintroduced to cylinders 560 via ports106a by control of valve 1100 to cinch" the base 34 up into contact withthe tube sheet 16. This step is of course unnecessary if the cinchingpressure was not previously released from cylinders 56a. Fingers 48bwith sleeves 50b are then fully raised by introducing air to cylinders56b through ports b. Because base portion 34 was cinched up into contactwith the tube sheet, fingers 48b will be inserted to the maximum extentin tubes 14. At this point, sleeves 50b will be expanded into grippingengagement with tubes 14 by admitting air to cylinders 56b through ports98b (or 98'b) by control of valve l02b. Thus, fingers 48b and sleeves50b are fully inserted in and are gripping tubes 14 of tube sheet 16,thereby recovering any slippage or spacing previously accruing betweenbase 34 and the tube sheet. It will be appreciated that fingers 48bmight have been raised or extended prior to, or concurrent with, the"cinching" operation with fingers 48a.

Sleeves 50a might now be relaxed, fingers 48a raised to their limit andsleeves 50a reexpanded into gripping engagement to obtain a fullyinserted configuration for all fingers 4S and sleeves 50. Alternatively,this repositioning of fingers 4811 might wait until those fingers aremoved to a new set of openings 18 during a stepping operation.

The earlier-mentioned half step operation, in which slider 46b was movedrelative to base 34, may be com pleted now by moving the base in thesame direction relative to slider 46b. This is accomplished by freeingand retracting fingers 48a and sleeves 50a and actuating piston cylindercombination 621) as was described for movement of fingers 48b.

One complete step of a slider 46 and base 34 relative to tube sheet 16,both parallel slider 46a and parallel slider 46b, has been describedincluding the cinching" operation. From this discussion, theinterrelationship of the cinching operation with the stepping operationshould be evident.

It will be understood that the embodiment shown and described herein ismerely illustrative and that changes may be made without departing fromthe scope of the invention as claimed.

What is claimed is:

l. A platform for support below a member comprising:

a. a base portion;

b.. at least two upwardly extending support means supportingly connectedto said base portion and independently reciprocable relative theretobetween raised and lowered positions and including remotely actuablemeans therewith for grippingly engaging said member to support a portionof the weight of said platform therefrom when in said engagement; and

c. remotely controllable means for selectively applying a force to saidsupport means relative to said base portion of a magnitude and directionto selectively move said support means either toward said raisedposition or said lowered position, even when said portion of platformweight is supported thereby.

2. The apparatus of claim I wherein said member includes openings in theundersurface thereof and said means for grippingly engaging said memberare sized for insertion in said openings and are expandable intofrictional engagement with a wall of openings.

3. A lifting mechanism for a platform self-supported below a memberhaving openings in the undersurface thereof comprising in combination:

a. a generally horizontally extending carriage base portion;

b. two upwardly extending cylinders carried by said base portion invertically fixed relationship thereto;

cv a first piston reciprocable in each said cylinder between raised andlowered positions and having a finger extending upwardly therefrom, saidfinger extending substantially above said base portion in said raisedposition and having a downwardly facing compression surface near theupper end thereof;

d. a second piston in each said cylinder concentrically disposed aboutsaid finger above said first piston and reciprocable relative theretoand to said cylinder between raised and lowered positions relative tosaid first piston and having an upwardly facing compression surfaceextending upwardly therefrom;

e. a resilient sleeve about each said finger between said upwardly anddownwardly facing compression surfaces for outward expansion intogripping engagement with the wall of a said opening when insertedthereinto and said second piston is in its raised position relative tosaid first piston;

f. first means for admitting driving fluid to each said cylinder belowsaid first piston at a pressure to raise said piston and finger;

g. second means for admitting driving fluid to each cylinderintermediate said first and second pistons at a pressure to move andmaintain said second piston at its said raised relative position tooutwardly expand said sleeve; and

h. third means for admitting driving fluid to each cylinder above saidsecond piston at a pressure to move said second piston downward relativeto said cylinder when said sleeve is in said gripping engagement,whereby said cylinder and carriage base portion are lifted towards saidmember.

4. The apparatus of claim 3 wherein said second means for admittingdriving fluid include a fluid conduit carried by said first piston andmovable relative to said cylinder in fluid sealed relationshiptherewith, one end of said conduit being connectable to a fluid sourceand the other end fluidly communicating with said cylinder intermediatesaid first and second pistons.

5. In a platform for suspended support below a mem her having holes inthe undersurface thereof and including two support means supportinglyconnected to a base portion of said platform and including means forgrippingly engaging said member, apparatus for lifting said base portionrelative to said undersurface comprising:

a. each said support means being reciprocable between raised and loweredlimits relative to said base portion;

b. said means for grippingly engaging said member moving with saidsupport means and sized for insertion into a said hole for selectiveengagement with a wall thereof to support the weight of said supportmeans and a portion of said base;

c. means for selectively actuating each said engaging means into and outof gripping engagement with said hole wall; and

(1. means for selectively applying a force to each said supporting meansrelative to said base of a magnitude and direction to reciprocate saidsupporting means toward said raised and said lowered limits, said forceapplied for said downward relative reciprocation of said support meansbeing sufficient to overcome the portion of weight of said basesupported by said support means, whereby to lift said base relative tosaid member.

6. The apparatus of claim 5 wherein at least one of said support meansis translated relative to said base in a direction parallel to said basefor moving said platform parallel said member undersurface.

7. The apparatus of claim 5 wherein said base includes two cylindersjoined thereto against upward and downward motion relative thereto; eachsaid support means comprises a finger extending upwardly from a piston,said piston being reciprocably mounted within a said cylinder; and saidforce applying means comprise means for applying a first force betweensaid piston and cylinder to move said piston in one direction relativeto said cylinder and base and a source of driving fluid admitted to saidcylinder for moving said piston in the other direction.

8. The apparatus of claim wherein said base includes two cylindersjoined thereto against substantial upward and downward motion relativethereto; each said support means comprise a finger extending upwardlyfrom a piston, said piston being reciprocably mounted within a saidcylinder; and said force applying means comprise a first source ofdriving fluid admitted to said cylinder above said piston in its raisedposition for moving said piston relatively downward and a second sourceof driving fluid admitted to said cylinder below said piston in itslower position for moving said piston relatively upward.

9. The apparatus of claim 8 wherein each said finger includes an upperjaw near its upper end; said hole engaging means comprise a resilientsleeve about said fin ger below said finger jaw said sleeve beingnormally diametrically smaller than a said hole and expandable intogripping engagement therewith; said actuating means for each saidengaging means comprise a lower jaw carried by a second piston slidablydisposed in a said cylinder about said finger above said finger pistonand below said resilient sleeve for reciprocation between a raised andlowered position relative to said finger piston to respectively expandand relax said sleeve; and a third source of driving fluid admitted tosaid cylinder between said finger piston and said second piston forrelatively moving said second piston to its raised position', and saidfirst source is admitted to said cylinder above said second piston insaid raised position of said finger piston.

10. The apparatus of claim 9 wherein the uppermost gripping surface ofeach said resilient sleeve is a certain distance above said carriagebase in said raised limit position of said support means; spacer meansposi' tioned to coact between said finger piston and said second pistonestablish a minimum spacing therebetween, said minimum spacing beingsubstantially that of said certain distance of said resilient sleeveuppermost gripping surface above said base; and said third source ofdriving fluid is admitted to said cylinder proximate the upper surfaceof said finger piston in its said raised position.

11. The apparatus of claim 10 wherein at least one of said cylinders intranslatable relative to said base in a direction parallel to said base,whereby to translate said support means relative to said base for movingsaid platform parallel to said member undersurface.

12. The apparatus of claim 9 wherein spacer means are positioned tocoact between said finger piston and said second piston to establish aminimum spacing therebetween and said third source of driving fluid isadmitted to said cylinder proximate the upper surface of said fingerpiston in its said raised limit position.

13. A method for supporting a platform closely adjacent the undersurfaceof a member having an opening in said undersurface, said platform havinga base portion and support means supportingly connected to said base andmovable relative thereto between raised and lowered positionsrespectively in response to raising and lowering forces appliedtherebetween and actuable into gripping engagement with a wall of saidopening when inserted therein, comprising the steps of;

a. positioning said platform near said member undersurface such thatsaid support means are inserted in said opening when in said raisedposition;

b. applying a raising force to move said support means to said raisedposition;

c. actuating said support means into gripping engagement with a wall ofsaid opening; and

d. applying a lowering force to said support means while maintainingsaid gripping engagement, said lowering force being of sufficientmagnitude to move said platform base portion upward to a limit closelyadjacent said member undersurface.

14. The method of claim 13 wherein said limit is established by contactof said base with said member.

15. The method of claim 13 including the step of maintaining saidsupport means lowering force follow ing arrival of said base at saidlimit.

16. The method of claim 13 wherein said member included a plurality ofopenings and said platform includes two support means independentlyraisable and lowerable and actuable into gripping engagement withdifferent of said openings and further comprising the steps of:

a. actuating one of said support means out of gripping engagement with asaid opening wall while maintaining the other in engagement;

b. applying a raising force to said one said support means whileapplying said lowering force to said other support means; and

c. actuating said one support means into gripping engagement with thewall of a said opening.

17. The method of claim 16 wherein a particular said support means istranslatable relative to said base in a direction substantially parallelto said base to align a support means with a different one of saidopenings, and further comprising the steps of:

a. applying a said lowering force to said one support means to move itto its lowered position following its said actuation out of grippingengagement; and

b. translating said particular support means relative to said base toalign said one lowered support means with a different one of saidopenings prior to applying said raising force thereto.

18. The method of claim 17 including the step of maintaining saidsupport means lowering force, following arrival of said base at saidlimit.

19. A method for lifting a platform dependently supported from a memberhaving openings in the under surface thereof. said platform including abase and two upwardly extending supporting means supportingly connectedthereto and independently movable relative thereto between raised andlowered positions for insertion in said raised position into saidopening and actuable into and out of gripping engagement with the wallof said opening when inserted thereinto to support said platform, bothsaid supporting means normally in grip ping engagement with said member,said method comprising the steps of:

a. actuating one of said supporting means out of gripping engagementwith said member;

b. moving said supporting means remaining in gripping engagementdownward relative to said base, whereby said base is raised relative tosaid member; and

c. actuating said previously removed supporting means into grippingengagement with said member.

20. The method of claim 19 wherein at least one of said supporting meansis movable relative to said base in a direction substantially parallelsaid base to align a 21. The method of claim 19 wherein said downwardmovement of said supporting means relative to said base is sufficient tolift said base to a maximum elevation proximate the undersurface of saidmember.

22. The method of claim 20 wherein said downward movement of saidsupporting means relative to said base is sufficient to lift said baseto a maximum elevation proximate the undersurface of said member.

l I III

1. A platform for support below a member comprising: a. a base portion;b. at least two upwardly extending support means supportingly connectedto said base portion and independently reciprocable relative theretobetween raised and lowered positions and including remotely actuablemeans therewith for grippingly engaging said member to support a portionof the weight of said platform therefrom when in said engagement; and c.remotely controllable means for selectively applying a force to saidsupport means relative to said base portion of a magnitude and directionto selectively move said support means either toward said raisedposition or said lowered position, even when said portion of platformweight is supported thereby.
 2. The apparatus of claim 1 wherein saidmember includes openings in the undersurface thereof and said means forgrippingly engaging said member are sized for insertion in said openingsand are expandable into frictional engagement with a wall of openings.3. A lifting mechanism for a platform self-supported below a memberhaving openings in the undersurface thereof comprising in combination:a. a generally horizontally extending carriage base portion; b. twoupwardly extending cylinders carried by said base portion in verticallyfixed relationship thereto; c. a first piston reciprocable in each saidcylinder between raised and lowered positions and having a fingerextending upwardly therefrom, said finger extending substantially abovesaid base portion in said raised position and having a downwardly facingcompression surface near the upper end thereof; d. a second piston ineach said cylinder concentrically disposed about said finger above saidfirst piston and reciprocable relative thereto and to said cylinderbetween raised and lowered positions relative to said first piston andhaving an upwardly facing compression surface extending upwardlytherefrom; e. a resilient sleeve about each said finger between saidupwardly and downwardly facing compression surfaces for outwardexpansion into gripping engagement with the wall of a said opening wheninserted thereinto and said second piston is in its raised positionrelative to said first piston; f. first means for admitting drivingfluid to each said cylinder below said first piston at a pressure toraise said piston and finger; g. second means for admitting drivingfluid to each cylinder intermediate said first and second pistons at apressure to move and maintain said second piston at its said raisedrelative position to outwardly expand said sleeve; and h. third meansfor admitting driving fluid to each cylinder above said second piston ata pressure to move said second piston downward relative to said cylinderwhen said sleeve is in said gripping engagement, whereby said cylinderand carriage base portion are lifted towards said member.
 4. Theapparatus of claim 3 wherein said second means for admitting drivingfluid include a fluid conduit carried by said first piston and movablerelative to said cylinder in fluid sealed relationship therewith, oneend of said conduit being connectable to a fluid source and the otherend fluidly communicating with said cylinder intermediate said first andsecond pistons.
 5. In a platform for suspended support below a memberhaving holes in the undersurface thereof and including two support meanssupportingly connected to a base portion of said platform and includingmeans for grippingly engaging said member, apparatus for lifting saidbase portion relative to said undersurface comprising: a. each saidsupport means being recIprocable between raised and lowered limitsrelative to said base portion; b. said means for grippingly engagingsaid member moving with said support means and sized for insertion intoa said hole for selective engagement with a wall thereof to support theweight of said support means and a portion of said base; c. means forselectively actuating each said engaging means into and out of grippingengagement with said hole wall; and d. means for selectively applying aforce to each said supporting means relative to said base of a magnitudeand direction to reciprocate said supporting means toward said raisedand said lowered limits, said force applied for said downward relativereciprocation of said support means being sufficient to overcome theportion of weight of said base supported by said support means, wherebyto lift said base relative to said member.
 6. The apparatus of claim 5wherein at least one of said support means is translated relative tosaid base in a direction parallel to said base for moving said platformparallel said member undersurface.
 7. The apparatus of claim 5 whereinsaid base includes two cylinders joined thereto against upward anddownward motion relative thereto; each said support means comprises afinger extending upwardly from a piston, said piston being reciprocablymounted within a said cylinder; and said force applying means comprisemeans for applying a first force between said piston and cylinder tomove said piston in one direction relative to said cylinder and base anda source of driving fluid admitted to said cylinder for moving saidpiston in the other direction.
 8. The apparatus of claim 5 wherein saidbase includes two cylinders joined thereto against substantial upwardand downward motion relative thereto; each said support means comprise afinger extending upwardly from a piston, said piston being reciprocablymounted within a said cylinder; and said force applying means comprise afirst source of driving fluid admitted to said cylinder above saidpiston in its raised position for moving said piston relatively downwardand a second source of driving fluid admitted to said cylinder belowsaid piston in its lower position for moving said piston relativelyupward.
 9. The apparatus of claim 8 wherein each said finger includes anupper jaw near its upper end; said hole engaging means comprise aresilient sleeve about said finger below said finger jaw, said sleevebeing normally diametrically smaller than a said hole and expandableinto gripping engagement therewith; said actuating means for each saidengaging means comprise a lower jaw carried by a second piston slidablydisposed in a said cylinder about said finger above said finger pistonand below said resilient sleeve for reciprocation between a raised andlowered position relative to said finger piston to respectively expandand relax said sleeve; and a third source of driving fluid admitted tosaid cylinder between said finger piston and said second piston forrelatively moving said second piston to its raised position; and saidfirst source is admitted to said cylinder above said second piston insaid raised position of said finger piston.
 10. The apparatus of claim 9wherein the uppermost gripping surface of each said resilient sleeve isa certain distance above said carriage base in said raised limitposition of said support means; spacer means positioned to coact betweensaid finger piston and said second piston establish a minimum spacingtherebetween, said minimum spacing being substantially that of saidcertain distance of said resilient sleeve uppermost gripping surfaceabove said base; and said third source of driving fluid is admitted tosaid cylinder proximate the upper surface of said finger piston in itssaid raised position.
 11. The apparatus of claim 10 wherein at least oneof said cylinders in translatable relative to said base in a directionparallel to said base, whereby to translate said support means relativeto said base for moving saId platform parallel to said memberundersurface.
 12. The apparatus of claim 9 wherein spacer means arepositioned to coact between said finger piston and said second piston toestablish a minimum spacing therebetween and said third source ofdriving fluid is admitted to said cylinder proximate the upper surfaceof said finger piston in its said raised limit position.
 13. A methodfor supporting a platform closely adjacent the undersurface of a memberhaving an opening in said undersurface, said platform having a baseportion and support means supportingly connected to said base andmovable relative thereto between raised and lowered positionsrespectively in response to raising and lowering forces appliedtherebetween and actuable into gripping engagement with a wall of saidopening when inserted therein, comprising the steps of: a. positioningsaid platform near said member undersurface such that said support meansare inserted in said opening when in said raised position; b. applying araising force to move said support means to said raised position; c.actuating said support means into gripping engagement with a wall ofsaid opening; and d. applying a lowering force to said support meanswhile maintaining said gripping engagement, said lowering force being ofsufficient magnitude to move said platform base portion upward to alimit closely adjacent said member undersurface.
 14. The method of claim13 wherein said limit is established by contact of said base with saidmember.
 15. The method of claim 13 including the step of maintainingsaid support means lowering force following arrival of said base at saidlimit.
 16. The method of claim 13 wherein said member included aplurality of openings and said platform includes two support meansindependently raisable and lowerable and actuable into grippingengagement with different of said openings and further comprising thesteps of: a. actuating one of said support means out of grippingengagement with a said opening wall while maintaining the other inengagement; b. applying a raising force to said one said support meanswhile applying said lowering force to said other support means; and c.actuating said one support means into gripping engagement with the wallof a said opening.
 17. The method of claim 16 wherein a particular saidsupport means is translatable relative to said base in a directionsubstantially parallel to said base, to align a support means with adifferent one of said openings, and further comprising the steps of: a.applying a said lowering force to said one support means to move it toits lowered position following its said actuation out of grippingengagement; and b. translating said particular support means relative tosaid base to align said one lowered support means with a different oneof said openings prior to applying said raising force thereto.
 18. Themethod of claim 17 including the step of maintaining said support meanslowering force, following arrival of said base at said limit.
 19. Amethod for lifting a platform dependently supported from a member havingopenings in the undersurface thereof, said platform including a base andtwo upwardly extending supporting means supportingly connected theretoand independently movable relative thereto between raised and loweredpositions for insertion in said raised position into said opening andactuable into and out of gripping engagement with the wall of saidopening when inserted thereinto to support said platform, both saidsupporting means normally in gripping engagement with said member, saidmethod comprising the steps of: a. actuating one of said supportingmeans out of gripping engagement with said member; b. moving saidsupporting means remaining in gripping engagement downward relative tosaid base, whereby said base is raised relative to said member; and c.actuating said previously removed supporting means into grippingengagement with said member.
 20. ThE method of claim 19 wherein at leastone of said supporting means is movable relative to said base in adirection substantially parallel said base to align a supporting meanswith a different said opening and further comprising the steps of: a.moving said one supporting means actuated out of gripping engagement toits said lowered position; b. moving said at least one supporting meansrelative to said base in said direction substantially parallel theretoto align said lowered supporting means with a different said opening;and c. moving said one supporting means actuated out of grippingengagement to its said raised position.
 21. The method of claim 19wherein said downward movement of said supporting means relative to saidbase is sufficient to lift said base to a maximum elevation proximatethe undersurface of said member.
 22. The method of claim 20 wherein saiddownward movement of said supporting means relative to said base issufficient to lift said base to a maximum elevation proximate theundersurface of said member.